The present invention is directed to a method and apparatus for making golf balls. More particularly, the invention is directed to a method and apparatus for forming multi-layered cores or golf balls that are substantially automated.
Generally, golf balls have been classified as solid balls or wound balls. Solid balls are generally comprised of a solid polymeric core and a cover. These balls are generally easy to manufacture, but are regarded as having limited playing characteristics. Wound balls are comprised of a solid or liquid-filled center surrounded by tensioned elastomeric material and a cover. Wound balls generally have good playing characteristics, but are more difficult to manufacture than solid balls.
The prior art is comprised of various golf balls that have been designed to provide optimal playing characteristics. These characteristics are generally the initial velocity and spin of the golf ball, which can be optimized for various players. For instance, certain players prefer to play a ball that has a high spin rate for playability. Other players prefer to play a ball that has a low spin rate to maximize distance. However, these balls tend to be hard feeling and difficult to control around the greens.
Manufacturers have molded layers around a solid center by placing a preformed center between two blocks of core material in a spherical compression mold, and closing the mold. This process, however, provides little control over the ultimate placement of the center within the golf ball core. Large variations in the location of the center can result.
The prior art also provides for the manufacture of double cover golf balls. This is generally accomplished by injection molding a first and then a second cover layer around a core. This system, however, requires complex injection molds, usually with retractable pins within the mold to properly position the core. Moreover, this system generally works better with thermoplastic materials.
Therefore, what is desired is a method and apparatus for molding multi-layer cores or multi-layer covers that ensures properly centered balls.
The present invention is directed to a method of making a golf ball core, comprising the steps of providing a plurality of centers; providing a top mold plate defining a first plurality of cavities, a bottom mold plate defining a second plurality of cavities corresponding to the first cavities, and a center mold plate disposed between the top and bottom mold plates and comprising a plurality of corresponding protrusions; forming a plurality of shells from a layer material by placing the layer material into the top and bottom mold plate cavities; and molding the layer material around the protrusions of the center plate by applying at least one of heat and pressure to the top and bottom mold plates such that the layer material has a different temperature than the mold plates; opening at least one mold plate from the center plate and placing the centers in the shells; and joining the top and bottom mold plates to join the shells around the centers.
Additionally, the step of forming a plurality of shells may further include the step of locating the top mold plate between the center and bottom mold plates so that the cavities in the top mold plate are adjacent to the center mold plate and the top, center and bottom mold plates are vertically aligned.
In one embodiment, the step of locating the top mold plate further includes vertically moving the center mold plate from an elevated position to a rotate position. The step of locating the top mold plate may further include vertically moving the top mold plate from a lower position to the rotate position. Following the step of applying heat and pressure to the top and bottom mold plates, the center mold plate may be vertically moved from the rotate position to the elevated position, and vertically moving the top mold plate from the rotate position to the lower position.
In another embodiment, the step of locating the top mold plate further includes horizontally moving the center mold plate from a first position substantially vertically unaligned with the top mold plate to a second position substantially vertically aligned with the top mold plate. Additionally, the step of forming a plurality of core hemispherical shells from elastomeric material further includes providing a lower elevator having a movable upper plate; and after applying heat and pressure to the top and bottom mold plates, separating the mold plates by moving the upper plate upward. The step of forming a plurality of shells may preferably include placing elastomeric material into the top and bottom mold plate cavities.
The present invention is also directed to a golf ball comprising a center and at least one cover layer, formed from the steps of providing a plurality of centers; providing a top mold plate defining a first plurality of cavities, a bottom mold plate defining a second plurality of cavities corresponding to the first cavities, and a center mold plate disposed between the top and bottom mold plates and comprising a plurality of corresponding protrusions; forming a plurality of shells from a layer material by placing the layer material into the top and bottom mold plate cavities; and molding the layer material around the protrusions of the center plate by applying at least one of heat and pressure to the top and bottom mold plates such that the layer material has a different temperature than the mold plates; opening at least one mold plate from the center plate and placing the centers in the shells; and joining the top and bottom mold plates to join the shells around the centers.